RE: Corrupt MARC records
At 16:58 7/05/2005, Andrew Houghton wrote: The code is off the top of my head and parts have been copied from a variety of Perl scripts I had hanging around. It isn't tested, but hopefully a start for your work. Thanks, Andy, there's a lot there that I can put to good use. Much more elegant code than I could have written off the top of MY head. At 21:10 7/05/2005, Ed Summers wrote: It's ironic that MARC::Record *used* to do what Andrew suggests: using split() rather than than substr() with the actual directory lengths. The reason for the switch was just as Andrew pointed out: the order of the tags in the directory is not necessarily the order of the field data. Has anybody ever seen a MARC record where the order of the field data wasn't the same as that of the entries in the directory? I'm not questioning the logic of reading a record using the field lengths and offsets, just wondering if anybody had ever seen this occur in the wild. I never have. Thanks again for your help and the confirmation that this kind of correction is a reasonable thing to do. Ron Ron Davies Information and documentation systems consultant Av. Baden-Powell 1 Bte 2, 1200 Brussels, Belgium Email: ron(at)rondavies.be Tel:+32 (0)2 770 33 51 GSM:+32 (0)484 502 393
Re: Corrupt MARC records
Ron Davies wrote: Has anybody ever seen a MARC record where the order of the field data wasn't the same as that of the entries in the directory? I'm not questioning the logic of reading a record using the field lengths and offsets, just wondering if anybody had ever seen this occur in the wild. I never have. I have although I can't recall where it came from. (It was some years ago) The problem was exacerbated because the program reading it assumed the directory and field sequence matched and was not flagging any errors. It was sometime later that users spotted some records were odd and it took a while to trace it back to this cause. Colin -- Colin Campbell Software Development Consultant Sirsi Ltd
Re: Corrupt MARC records
I wondered if any of you had run into similar problems, or if you had any thoughts on how to tackle this particular issue. It's ironic that MARC::Record *used* to do what Andrew suggests: using split() rather than than substr() with the actual directory lengths. The reason for the switch was just as Andrew pointed out: the order of the tags in the directory is not necessarily the order of the field data. If you need to you could try downloading MARC::Record v1.17 and try using that. Or you could roll your own code and cut and paste it everywhere like Andrew ;-) //Ed
RE: Corrupt MARC records
Most MARC utilities like MARC::Record depend upon the actual directory lengths and having well formed structure. Isn't that what standards are for? But sometimes you really do get badly formed MARC records and need to recover the data. The presented code does have two caveats, which I pointed out and Ed reiterates. The directory *must* be in the same order as the fields. However, even if the fields are not in the same order as the directory, code could be written to take that into account so long as you can make the assumption that the start positions for each directory entry give the nearest position to the data. If we take the directory and sort on the start position field, we will have the directory in the order necessary for extraction by the presented code. Of course, you would probably want to keep track of the original directory and the sorted directory order so you can output the MARC record with the fields in the same order as the original. Things are never ideal when you have corrupt MARC records... Andy. -Original Message- From: Ed Summers [mailto:[EMAIL PROTECTED] Sent: Saturday, May 07, 2005 3:11 PM To: perl4lib@perl.org Subject: Re: Corrupt MARC records I wondered if any of you had run into similar problems, or if you had any thoughts on how to tackle this particular issue. It's ironic that MARC::Record *used* to do what Andrew suggests: using split() rather than than substr() with the actual directory lengths. The reason for the switch was just as Andrew pointed out: the order of the tags in the directory is not necessarily the order of the field data. If you need to you could try downloading MARC::Record v1.17 and try using that. Or you could roll your own code and cut and paste it everywhere like Andrew ;-) //Ed
